1. Field of the Invention
The present invention relates to image processing, and particularly, to an object image detection device and method able to rapidly detect an object image from an input image.
2. Description of the Related Art
In recent years, usage of an object image detection technique has been widely spread. Here, the “object image detection technique” represents a technique of detecting objects such as faces or cars, from an image such as a picture, a still image, or a video image.
For example, this technique is described in U.S. Pat. No. 7,099,510 (hereinafter, referred to as “reference 1”), U.S. Pat. No. 7,020,337 (hereinafter, referred to as “reference 2”), and “Robust Real-Time Face Detection”, P. Viola, M. J. Jones, International Journal of Computer Vision, vol. 57, pp. 137-154, May 2004 (hereinafter, referred to as “reference 3”).
When applying the object image detection technique in the related art to a digital camera or other portable digital devices, the following problems occur. Namely, these portable digital devices have processors of low clock frequencies and memories of small capacities, thus lack high computation capability; as a result, the object image detection technique in the related art, which requires high computational capability, cannot be applied to these devices directly.
In addition, reference 1 and reference 2 disclose techniques of extracting image blocks from a specified image area of an input image, determining whether the specified image area is the desired object image, and, after obtaining all the object images, outputting these object images. However, reference 1 and reference 2 do not disclose a technique for rapid image detection. Usually, for example, when using digital cameras having functions of object image detection, users wish to observe detected images on a monitor as soon as possible. Therefore, the users require a technique able to rapidly detect object images and display the detected images to users even when the devices in use do not have high computational capability.